Hello!

Thank you for your wonderful question on place value. Also I apologize in the answering delay, but looking into your question deeper and talking to Dr. Joan Cotter on what her thoughts were, and she came up with this delightful insight!

Your son may need more help in naming these higher numbers. A good way is to play the "Can You Find?" games. The original game is in Lesson 26 with variations in Lessons 32, 41, and 43. For a new variation, ask him to lay out the place-value cards. Then ask for the sum of two numbers, such as "Can You Find 200 plus 300?" [500 card] or "Can You Find 200 plus 1?" [200 card and the 1 card]

I personally hadn't thought of using the "Can You Find?" game, but this works wonderful with your place value question.

I hope this works well for your son! Please let us know if you have any additional questions!

Thank you,

Cassie